Thirty-two patients were studied to determine the comparative efficacy of pancreatic CT-scanning and ultrasound in diagnosing pancreatic cancer, and in following results of therapy. Of 17 patients studied prospectively, 12 are evaluable (the other five include four patients with adenocarcinoma of unknown origin, and one patient has not had laparotomy). Four had pancreatic cancer identified correctly by both tests pre-operatively. Of eight patients without pancreatic cancer, six had other intraabdominal pathology (benign or malignant), shown on one or both tests. Sensitivity for detection of pancreatic cancer or peri-pancreatic pathology was 91% for CT and 100% for ultrasound. Thirteen of 17 patients with proven pancreatic cancer studied post-operatively with serial tests are available for response to therapy (radiation and/or chemotherapy). Seven patients had tumor regression, detectable by CT scan in 5 and ultrasound in 3. Six patients had progressive disease, documented definitely by one CT series, and equivocally in one ultrasound series. The overall detection rate of pancreatic masses is 95% scan and 89% for ultrasound. No difference was demonstrated in usefulness of CT scanning vs. ultrasound in detecting pancreatic cancer. CT-scanning, with superior visualization of organ boundaries and retroperitoneal spaces, is very useful in planning radiation ports and dosimetry for locally unresectable pancreatic cancer.